Self inductance, Physics

Self inductance:

When current through a coil changes, the changing flux induces an emf that opposes the current flow.  This emf is the result of self inductance and is called 'back emf'.  The term 'self inductance' is often replaced merely by inductance.  The value of back emf is given by:

          E  =  -L x dl/dt  

Where L is the inductance in henries, and dl/dt the rate of change of current.

The minus indicates back emf.

The unit of inductance is the henry and is based on the equation.  If current changing at a rate of 1 amp a second induces an emf of 1 volt then the inductance is 1 henry. 

All circuits have inductance even a straight conductor, but if a straight piece of wire is formed into a coil the number of flux linkages increases and so does the inductance.

A further increase in inductance is achieved by increasing the flux density.  This depends on the area, the length of the coil and the permeability of material in which flux is established,

Thus,                  L    2257_self inductance.png=   Henries

                   N      =  Number of Turns

                   μo μr          =  Absolute Permeability

                   A       =  Area in square metres

                   I        =  Length of coil in metres (not wire)

As  reluctance (S) =  1903_self inductance1.png        μo μr A  =1/S       and     L  = N2/S

Also by transposition of E  =  -L  ×  dl/dt

          L  =  -E  ×  dl/dt

 

Posted Date: 9/13/2012 6:17:52 AM | Location : United States







Related Discussions:- Self inductance, Assignment Help, Ask Question on Self inductance, Get Answer, Expert's Help, Self inductance Discussions

Write discussion on Self inductance
Your posts are moderated
Related Questions
The width of the central bright band of a diffraction pattern is 2.9 cm. Laser light of unknown wavelength passes through a single slit that is 0.042 mm wide and onto a screen

Describe an echo. What is the minimum distance needed to form an echo. Write its application.

With the help of neat & labelled diagram. Explain the principle & working of a moving coil galvanometer. What is importance of radial magnetic field.

What is geocentric? It is a science where the earth is the center of the solar system and the other planets and the sun revolve around the earth. Though, most scientists say t

2-Point Source Interference Changing Wavelength The intrusion of two sets of circular waves along with the similar frequency and the similar amplitude results within a standing

Why nuclear fission preceeds nuclear fusion?

Explain the applications of polarization of light?  Write any four applications of interference of light. Illustrate how plane polarized light obtained by reflection.

Q. Define Fermi energy. Write down the expression for Fermi Dirac distribution law. Deduce an expression for Fermi energy of a system of free particles. Sol. The Fermi Energy

A boat can travel at a speed of 3 m s -1 on still water. A boatman needs to cross a river whilst covering the shortest possible distance. In what direction should he row with resp

Draw and explain V-I characteristics of constant voltage and constant current sources. Ans: V-I Characteristics of Constant Voltage Source: A voltage source that has very low